Alkyl length effects on solid-state fluorescence and mechanochromic behavior of small organic luminophores

The introduction of alkyl chains to the periphery of the conjugated skeleton of organic chromophores is generally to improve their solubility. However, a number of investigations show that the length of alkyl chains could affect significantly the solid-state molecular packing modes and optical and electronic properties, and thereby alkyl chains could play functional roles in tuning and altering the solid-state aggregation behavior and optoelectronic properties. While there have been a variety of reports on the impact of alkyl chains on organic field-effect transistor and photovoltaic performances, recently increasing interest has been paid to how the alkyl length affects the emission and stimuli responsive properties of organic fluorescent materials. This review focuses on alkyl length effects on solid-state fluorescence and mechanochromic behaviors, and the purpose is to arouse one's further attention to the alkyllength effect in the design, synthesis and structure-property investigation of organic optoelectronic materials.